A notebook-sized personal computer and an on-vehicle closable type or retractable display apparatus installed on the ceiling of an automobile vehicle are each composed of a first casing having an image display surface such as a liquid crystal panel and a second casing which openably and closably supports the first casing with hinges. The first casing of such a retractable display apparatus includes a frame cover housing a display member such as a liquid crystal panel and a back cover, and in general, both the covers are combined by screw-holding in consideration of disassembly under fault conditions. However, the screw holding structure results the increased number of man-hours because of the large number of screws and requires sheet-covering over the exposed screw-holding area for concealing the area because of its poor appearance, thus causing an increase in the cost. Therefore, nowadays, included in such retractable display apparatuses are display apparatuses employing an engaging means such as an engaging claw or pawl structure between edge portions where both the covers are butting each other (referred to as a “butt edge portion” hereinafter) (e.g., see Patent Document 1). Since the engaging claw can be molded integral with the casing upon fabricating a casing made of a synthetic resin, the number of parts can be reduced to facilitate an assembly thereof, and also provide a design advantage thereof. Thus, today, engaging claw structures are often used. Further, in the case of employing an engaging claw structure, a notch hole may be formed in a butt edge portion where an engaging means of two covers for constituting a casing is provided, and a tool is inserted into the notch hole to release a flexible piece having an engaging claw from its lock section, thus disassembling easily an assembled casing (see Patent Document 2, for instance).    Patent Document 1: JP-A-9-246772    Patent Document 2: JP-A-2007-013249
As discussed above, the casing structure, where the two covers made of a synthetic resin are combined and assembled by the engaging means molded integral with the casing, requires a hole into which a tool is inserted, for releasing the engaging state at the time of repair. Such a insertion hole is designed to be comparatively small size for consumer products or the like; however, the hole is sometimes conspicuous for its exposure on the exterior. There can arise a problem that a user disassembles the casing by inserting a screw driver or the like thereinto as the user pleases and modifies the interior of the apparatus. Therefore, it is required to provide a hole into which a tool is inserted at a place as unobtrusive as possible.
The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a retractable display apparatus having a casing structure where a hole into which a tool for disassembling the casing is inserted is provided at the place that cannot be easily found.